// @(#)root/base:$Id$
// Author: Rene Brun   02/09/2000

/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

/** \class TTask
TTask is a base class that can be used to build a complex tree of Tasks.
Each TTask derived class may contain other TTasks that can be executed
recursively, such that a complex program can be dynamically built and executed
by invoking the services of the top level Task or one of its subtasks.

Use the TTask::Add function to add a subtask to an existing TTask.
To execute a TTask, one calls the ExecuteTask function. ExecuteTask will
call recursively:

  - the TTask::Exec function of the derived class
  - TTask::ExecuteTasks to execute for each task the list of its subtasks.

If the top level task (see example below) is added to the list of Root
browsable objects, the tree of tasks can be visualized by the Root browser.
The browser can be used to start a task, set break points at the beginning
of a task or when the task has completed. At a breakpoint, data structures
generated by the execution up this point may be inspected asynchronously
and then the execution can be resumed by selecting the "Continue" function
of a task.
//
A Task may be active or inactive (controlled by TTask::SetActive).
When a task is not active, its sub tasks are not executed.
//
A TTask tree may be made persistent, saving the status of all the tasks.
//
The Root browser's picture below has been generated by executing
the following script:
~~~ {.cpp}
{
   TTask *aliroot  = new TTask("aliroot","ALICE reconstruction main task");
   TTask *geominit = new TTask("geomInit","Initialize ALICE geometry");
   TTask *matinit  = new TTask("matInit","Initialize ALICE materials");
   TTask *physinit = new TTask("physInit","Initialize Physics processes");
   TTask *tracker  = new TTask("tracker","Track reconstruction manager");
   TTask *tpcrec   = new TTask("tpcrec","TPC reconstruction");
   TTask *itsrec   = new TTask("itsrec","ITS reconstruction");
   TTask *muonrec  = new TTask("muonRec","Muon Reconstruction");
   TTask *phosrec  = new TTask("phosRec","Phos Reconstruction");
   TTask *richrec  = new TTask("richRec","Rich Reconstruction");
   TTask *trdrec   = new TTask("trdRec","TRD Reconstruction");
   TTask *globrec  = new TTask("globRec","Global Track Reconstruction");
   TTask *pstats   = new TTask("printStats","Print Run Statistics");
   TTask *run      = new TTask("run","Process one run");
   TTask *event    = new TTask("event","Process one event");
   aliroot->Add(geominit);
   aliroot->Add(matinit);
   aliroot->Add(physinit);
   aliroot->Add(run);
   run->Add(event);
   event->Add(tracker);
   event->Add(muonrec);
   event->Add(phosrec);
   event->Add(richrec);
   event->Add(trdrec);
   event->Add(globrec);
   tracker->Add(tpcrec);
   tracker->Add(itsrec);
   run->Add(pstats);

   gROOT->GetListOfBrowsables()->Add(aliroot,"aliroot");
   new TBrowser;
}
~~~
\image html base_tasks.png
*/

#include "Riostream.h"
#include "TTask.h"
#include "TBrowser.h"
#include "TROOT.h"
#include "TRegexp.h"

TTask *TTask::fgBeginTask  = 0;
TTask *TTask::fgBreakPoint = 0;

ClassImp(TTask)

////////////////////////////////////////////////////////////////////////////////
/// Default constructor invoked when reading a TTask object from a file.

TTask::TTask()
{
   fHasExecuted = kFALSE;
   fActive      = kTRUE;
   fBreakin     = 0;
   fBreakout    = 0;
   fTasks       = 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Standard constructor.

TTask::TTask(const char* name, const char *title)
      : TNamed(name,title)
{
   fHasExecuted = kFALSE;
   fActive      = kTRUE;
   fBreakin     = 0;
   fBreakout    = 0;
   fTasks       = new TList();
}

////////////////////////////////////////////////////////////////////////////////
/// Assignment operator.

TTask& TTask::operator=(const TTask& tt)
{
   if(this!=&tt) {
      TNamed::operator=(tt);
      fTasks->Delete();
      TIter next(tt.fTasks);
      TTask *task;
      while ((task = (TTask*)next())) {
         fTasks->Add(new TTask(*task));
      }
      fOption=tt.fOption;
      fBreakin=tt.fBreakin;
      fBreakout=tt.fBreakout;
      fHasExecuted=tt.fHasExecuted;
      fActive=tt.fActive;
   }
   return *this;
}

////////////////////////////////////////////////////////////////////////////////
/// Copy constructor.

TTask::TTask(const TTask &other) : TNamed(other)
{
   fTasks = new TList();
   TIter next(other.fTasks);
   TTask *task;
   while ((task = (TTask*)next())) {
      fTasks->Add(new TTask(*task));
   }
   fOption = other.fOption;
   fBreakin = other.fBreakin;
   fBreakout = other.fBreakout;
   fHasExecuted = kFALSE;
   fActive = other.fActive;
}

////////////////////////////////////////////////////////////////////////////////
/// Delete a task and its subtasks.

TTask::~TTask()
{
   if (!fTasks) return;
   fTasks->Delete();
   delete fTasks;
}

////////////////////////////////////////////////////////////////////////////////
/// Abort current tree of tasks.
/// After this call, the tree of tasks is ready to be executed again.
/// The application must take care of cleaning data structures created
/// by previous executions.

void TTask::Abort()
{
   if (!fgBeginTask) {
      printf(" Nothing to abort: No task currently running\n");
      return;
   }
   CleanTasks();
   fgBeginTask  = 0;
   fgBreakPoint = 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Browse the list of tasks.
/// It is recommended to add the top level task to the list of
/// ROOT browsables by:
/// ~~~{.cpp}
///    gROOT->GetListOfBrowsables()->Add(myTopLevelTask)
/// ~~~

void TTask::Browse(TBrowser *b)
{
   fTasks->Browse(b);
}

////////////////////////////////////////////////////////////////////////////////
/// Reset tasks state: breakpoints and execute flags
/// also invokes the Clear function of each task to clear all data
/// structures created by a previous execution of a task.

void TTask::CleanTasks()
{
   if (fBreakin)  fBreakin  = 1;
   if (fBreakout) fBreakout = 1;
   fHasExecuted = kFALSE;
   Clear();
   TIter next(fTasks);
   TTask *task;
   while((task=(TTask*)next())) {
      task->CleanTasks();
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Recursively call the Clear function of this task and its subtasks.
/// The Clear function must be implemented for each derived class
/// to clear all data structures created by a previous execution of a task.
/// This function is automatically called by the CleanTasks function.

void TTask::Clear(Option_t *)
{
}

////////////////////////////////////////////////////////////////////////////////
/// Resume execution at the current break point.

void TTask::Continue()
{
   if (!fgBeginTask) {
      printf(" No task to continue\n");
      return;
   }
   fgBreakPoint = 0;

   fgBeginTask->ExecuteTasks(fOption.Data());

   if (!fgBreakPoint) {
      fgBeginTask->CleanTasks();
      fgBeginTask = 0;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Dummy Execute.
/// This function must be redefined in the derived classes.

void TTask::Exec(Option_t *)
{
}

////////////////////////////////////////////////////////////////////////////////
/// Execute main task and its subtasks.
/// When calling this function, the Exec function of the corresponding class
/// is invoked, then the list of its subtasks is executed calling recursively
/// all the subtasks, etc.
///
/// The option parameter may be used to select different execution steps
/// within a task. This parameter is passed also to all the subtasks.

void TTask::ExecuteTask(Option_t *option)
{
   if (fgBeginTask) {
      Error("ExecuteTask","Cannot execute task:%s, already running task: %s",GetName(),fgBeginTask->GetName());
      return;
   }
   if (!IsActive()) return;

   fOption = option;
   fgBeginTask = this;
   fgBreakPoint = 0;

   if (fBreakin) return;
   if (gDebug > 1) {
      TROOT::IndentLevel();
      std::cout<<"Execute task:"<<GetName()<<" : "<<GetTitle()<<std::endl;
      TROOT::IncreaseDirLevel();
   }
   Exec(option);

   fHasExecuted = kTRUE;
   ExecuteTasks(option);

   if (gDebug > 1) TROOT::DecreaseDirLevel();
   if (fBreakout) return;

   if (!fgBreakPoint) {
      fgBeginTask->CleanTasks();
      fgBeginTask = 0;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Execute all the subtasks of a task.

void TTask::ExecuteTasks(Option_t *option)
{
   TIter next(fTasks);
   TTask *task;
   while((task=(TTask*)next())) {
      if (fgBreakPoint) return;
      if (!task->IsActive()) continue;
      if (task->fHasExecuted) {
         task->ExecuteTasks(option);
         continue;
      }
      if (task->fBreakin == 1) {
         printf("Break at entry of task: %s\n",task->GetName());
         fgBreakPoint = this;
         task->fBreakin++;
         return;
      }

      if (gDebug > 1) {
         TROOT::IndentLevel();
         std::cout<<"Execute task:"<<task->GetName()<<" : "<<task->GetTitle()<<std::endl;
         TROOT::IncreaseDirLevel();
      }
      task->Exec(option);
      task->fHasExecuted = kTRUE;
      task->ExecuteTasks(option);
      if (gDebug > 1) TROOT::DecreaseDirLevel();
      if (task->fBreakout == 1) {
         printf("Break at exit of task: %s\n",task->GetName());
         fgBreakPoint = this;
         task->fBreakout++;
         return;
      }
   }
}

////////////////////////////////////////////////////////////////////////////////
/// List the tree of tasks.
/// Indentation is used to identify the task tree.

void TTask::ls(Option_t *option) const
{
   TROOT::IndentLevel();
   std::cout <<GetName()<<"\t"<<GetTitle()<<std::endl;
   TROOT::IncreaseDirLevel();

   TString opta = option;
   TString opt  = opta.Strip(TString::kBoth);

   TRegexp re(opt, kTRUE);

   TObject *obj;
   TIter nextobj(fTasks);
   while ((obj = (TObject *) nextobj())) {
      TString s = obj->GetName();
      if (s.Index(re) == kNPOS) continue;
      obj->ls(option);
   }
   TROOT::DecreaseDirLevel();
}